The purpose of the GART Protocol is to determine the short-term effects of using plasma genotypic antiretroviral resistance testing (GART) in the management of antiretroviral therapy for antiretroviral-experienced patients failing while on one of the following four regimens: 1) ZDV + 3TC + IDV; 2) ZDV + 3TC +SQV; 3) ZDV + 3TC + RTV; or 4) d4T + 3 TC+ IDV. This is a multi-center randomized trial. An equal number of patients will be randomized in each stratum. Accrual is expected to take 24 weeks. Each patient will be followed for 12 weeks after randomization. Thus, the total study duration is expected to be 36 weeks.